Understanding Moon Photography: Debunking Focal Length Myths

Recently, there has been a misunderstanding about the capabilities of camera lenses for photographing the moon. Some believe that only a specific focal length can achieve accurate imaging of the moon. However, the concept of focal length and how lenses work is far more nuanced than that. This article aims to clarify these misconceptions and showcase the capabilities of modern camera technology in moon photography.

The Misconception: Focal Length and Moon Photography

A common misunderstanding is that a 380,000-kilometer (the distance to the moon) focal length is required to focus on the moon. However, as explained by experts, this is simply not true. The focal length of a lens determines the distance from the lens to the sensor when an object is in focus, affecting the magnification and field of view, but not the ability to focus on an object.

It is indeed possible to accurately image the moon with a much shorter focal length lens, using modern technology and techniques. This is demonstrated in the examples provided below, showcasing photos taken with relatively standard camera equipment (including a Sony A7R IV and Sony lenses).

Understanding Focal Length

What is Focal Length?

Focal length refers to the distance (measured in millimeters) between the lens and the camera sensor when the image is in focus. It is important to note that the focal length does not limit the focus distance; any object that is more than a few meters away will be in focus, regardless of the focal length.

A simple diagram can illustrate this: The objective lens focuses light from a distant object to a point. This focusing is based on the design of the lens and is independent of the distance to the object. For distances greater than a few meters, the entire object will be in focus, regardless of how far away it is.

Practical Applications

Anyone with a camera and a decent telephoto lens or telescope can photograph the moon with reasonable accuracy. For example, the photo below was taken with a Sony A7R IV camera and a Sony FE 200-600mm zoom lens. The moon's craters are clearly visible, confirming the accurate imaging capability of the setup.

Modern Technology and Astrophoto Imaging

Modern technology has allowed us to combine astronomical observations at great distances to create the equivalent of a telescope of huge dimension. This technique significantly enhances the resolving power and detail of captured images.

The examples provided below further demonstrate the capabilities of modern camera technology. Both photos were taken using an off-the-shelf Sony A7R IV 61-megapixel mirrorless camera. The first photo was taken with the Sony FE 200-600mm zoom lens, and the second with the Sony 600mm prime lens with a 1.4x teleconverter, effectively making it an 840mm lens. Despite the shorter focal length, the images are detailed and accurate, showcasing the precision of modern camera systems.

For ultimate clarity, it is recommended to shoot multiple images and stack them in Photoshop or a dedicated astrophoto image stacking program. This technique further enhances the detail and accuracy of the final image.

In conclusion, while the concept of focal length is important in understanding how lenses work, it does not limit the ability to photograph the moon accurately. Modern technology and techniques enable anyone with the right equipment to capture detailed images of the moon with ease.